<html>  
  <head>  
      <meta charset="UTF-8">  
      <title>js简单时分秒倒计时</title> 

 <style type="text/css">
 
		 body{
		  background:url(img/back.jpg) no-repeat left top / 100% 100%;overflow: hidden;
		  background-size:100%;
		}
        
        div{
            width: 600px;
            height: 200px;
        }
        .center-in-center{
		    background:url(/img/back.jpg) no-repeat left top / 100% 100%;overflow: hidden;
		    font-size:52px;
            position: absolute;
            top: 50%;
            left: 50%;
            -webkit-transform: translate(-50%, -50%);
            -moz-transform: translate(-50%, -50%);
            -ms-transform: translate(-50%, -50%);
            -o-transform: translate(-50%, -50%);
            transform: translate(-50%, -50%);
        }
    </style>	  
      <script type="text/javascript">  
          function countTime() {  
             //获取当前时间  
              var date = new Date();  
              var now = date.getTime();  
             //设置截止时间  
             var str="2019/1/14 00:00:00";
             var endDate = new Date(str); 
             var end = endDate.getTime();  
             
             //时间差  
             var leftTime = end-now; 
             //定义变量 d,h,m,s保存倒计时的时间  
             var d,h,m,s;  
             if (leftTime>=0) {  
                 d = Math.floor(leftTime/1000/60/60/24);  
                 h = Math.floor(leftTime/1000/60/60%24);  
                 m = Math.floor(leftTime/1000/60%60);  
                s = Math.floor(leftTime/1000%60);                     
             }  
             //将倒计时赋值到div中  
             document.getElementById("_d").innerHTML = d+"天";  
             document.getElementById("_h").innerHTML = h+"时";  
             document.getElementById("_m").innerHTML = m+"分";  
             document.getElementById("_s").innerHTML = s+"秒";  
             //递归每秒调用countTime方法，显示动态时间效果  
             setTimeout(countTime,1000);  
   
         }  
     </script>  
 </head >  
 <body onload="countTime()" >  
     <div class="center-in-center">  
         <span id="_d">00</span>  
         <span id="_h">00</span>  
         <span id="_m">00</span>  
         <span id="_s">00</span>  
     </div>  
 </body>  
 </html>